Using Task Placement Strategies - AWS ECS Tutorial

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Task placement strategies are an important feature in Amazon Elastic Container Service (ECS) that allow you to control how tasks are distributed across the instances in your ECS cluster. By using task placement strategies, you can optimize resource utilization, improve fault tolerance, and enhance performance. This tutorial will guide you through the process of using task placement strategies in ECS.

Using Task Placement Strategies

To use task placement strategies in Amazon ECS, follow these steps:

  1. Define Task Placement Constraints: Specify constraints that influence the placement of tasks, such as the instance type, availability zone, or custom attributes.
  2. Create a Task Placement Strategy: Define a task placement strategy that combines one or more placement constraints. ECS provides built-in strategies like "spread" and "binpack" or allows you to create custom strategies.
  3. Configure the Task Definition: Set the task placement strategy on your task definition by specifying the strategy name or ARN.
  4. Launch and Monitor Tasks: Launch tasks using the updated task definition and monitor their placement to ensure they adhere to the defined placement strategy.

Example: Using a Task Placement Strategy

Here's an example of using a task placement strategy in an ECS task definition:

"family": "my-task-definition",
"networkMode": "awsvpc",
"taskRoleArn": "arn:aws:iam::1234567890:role/my-task-role",
"executionRoleArn": "arn:aws:iam::1234567890:role/my-execution-role",
"requiresCompatibilities": ["FARGATE"],
"cpu": "512",
"memory": "1024",
"containerDefinitions": [
"name": "my-container",
"image": "my-container-image:latest",
"portMappings": [
"containerPort": 80,
"protocol": "tcp"
"cpu": 256,
"memoryReservation": 512,
"logConfiguration": {
"logDriver": "awslogs",
"options": {
"awslogs-group": "my-log-group",
"awslogs-region": "us-east-1",
"awslogs-stream-prefix": "my-stream-prefix"
"placementConstraints": [
"type": "memberOf",
"expression": "attribute:ecs.instance-type =~ t2.*"
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Common Mistakes

  • Not considering the specific resource requirements of your tasks when defining placement constraints, which can result in suboptimal resource utilization.
  • Using too many placement constraints, leading to limited placement options and potentially impacting task scheduling.
  • Not monitoring the effectiveness of the chosen placement strategy and failing to make adjustments if tasks are not being placed optimally.
  • Overlooking the impact of placement strategies on task availability and fault tolerance, potentially concentrating tasks in a single instance or availability zone.
  • Ignoring the instance attribute requirements when defining placement constraints, which can result in unexpected task placement behavior.

Frequently Asked Questions

  1. Can I use multiple placement strategies for a task definition?

    No, you can only specify a single placement strategy per task definition. However, a placement strategy can consist of multiple placement constraints.

  2. Can I create custom placement strategies?

    Yes, you can create custom placement strategies by combining one or more placement constraints and specifying the strategy as part of the task definition.

  3. How does the "spread" placement strategy work?

    The "spread" strategy evenly distributes tasks across available instances, maximizing fault tolerance by ensuring tasks are placed on different instances.

  4. What is the "binpack" placement strategy?

    The "binpack" strategy aims to maximize resource utilization by packing tasks onto instances using the least amount of unused resources.

  5. Can I use task placement strategies with EC2 launch type and Fargate launch type?

    Yes, task placement strategies can be used with both EC2 and Fargate launch types in Amazon ECS.


Task placement strategies are a powerful tool in Amazon Elastic Container Service (ECS) that allow you to control how tasks are distributed across instances in your cluster. By understanding how to define placement constraints, create placement strategies, and configure task definitions, you can optimize resource utilization and improve the performance and fault tolerance of your applications in ECS.